linux-kernel - Re: [feature] automatically detect hung TASK

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Date:	Sun, 2 Dec 2007 19:59:45 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [feature] automatically detect hung TASK_UNINTERRUPTIBLE tasks


* Andi Kleen <andi@...stfloor.org> wrote:

> Ingo Molnar <mingo@...e.hu> writes:
> 
> > this patch extends the soft-lockup detector to automatically
> > detect hung TASK_UNINTERRUPTIBLE tasks. Such hung tasks are
> > printed the following way:
> 
> That will likely trigger anytime a hard nfs/cifs mount loses its 
> server for 120s. To make this work you would need a new 
> TASK_UNINTERRUPTIBLE_EXTERNAL_EVENT or similar and mark all the places 
> which depend on those.

TASK_KILLABLE should be the right solution i think.

> I've also seen kernel modules that use semaphores like wait queues 
> While that gives a little funny results (high load average) it worked 
> so far, until this patch.

it still works with this patch of course. With a funny results like high 
load average _AND_ a clear debug message that tells us (and the user) 
where that high load average comes from.

	Ingo
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